Fictive respiratory rhythm in the isolated brainstem of frogs |
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Authors: | H A McLean N Kimura N Kogo S F Perry J E Remmers |
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Institution: | (1) Departments of Medicine and Physiology, Faculty of Medicine, University of Calgary, T2N 4N1 Calgary, AB, Canada;(2) Present address: INSERM Unité 29, Hôpital de Port-Royal, 123 Boulevard de Port-Royal, F-75674 Paris Cedex 14, France;(3) Present address: Jikei University School of Medicine, 3-25-8 Nishi-shinbashi, Minato-ku, 105 Tokyo, Japan;(4) Present address: St. Louis University School of Medicine, 1402 S. Grand Boulevard, 63104 St. Louis, MO, USA;(5) Present address: Zoologisches Institut Rheinische Friedrich Wilhelms-Universität Bonn, D-53115 Bonn, Germany |
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Abstract: | Spontaneous rhythmically bursting activity was recorded from the trigeminal, vagal and hypoglossal nerve roots of the isolated brainstem from the frogsRana catesbeiana andRana pipiens superfused with a bicarbonate-free HEPES-buffer solution. Burst frequency, burst duration and the activity profile of the spontaneous neural discharges in vitro resembled those of a less radical preparation, the decerebrate, fictively breathing frog. After complete midsagittal section, each half of the isolated brainstem generated its own rhythmic neural activity which resembled that of the intact isolated brainstem. The spontaneous activity generated within each half of the brainstem is probably coordinated by decussating axons or by groups of neurons located along the midline of the brainstem. Our results suggest that these coordinating entities extend the length of the brainstem (in a rostro-caudal dimension) and the degree of contact rather than the location of the contact between the two halves of the brainstem determines the synchronization of the right and left halves. Burst frequency of both the intact and hemisected brainstem preparation was decreased by alkaline challenge and increased by acid challenge. We conclude that this endogeneous rhythmic activity represents the efferent motor output underlying lung ventilation in these animals.Abbreviations
EMG
electromyogram
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ENG
electroneurogram
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V
trigeminal nerve
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Vmd
mandibular branch of trigeminal nerve
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X
vagal nerve
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X1
laryngeal branch of vagal nerve
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H
hypoglossal nerve
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Hsh
sternohyoid branch of hypoglossal nerve
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Hm
main branch of hypoglossal nerve |
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Keywords: | Neural control of breathing Amphibian Isolated brainstem Respiration Pattern generation |
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